Hydrotreating hydrocarbon feeds in an ebullating bed reactor

ABSTRACT

The present invention relates to the use of a catalyst comprising an extruded essentially alumina-based support, constituted by a plurality of juxtaposed agglomerates and partially in the form of packs of flakes and partially in the form of needles, and optionally comprising at least one catalytic metal or a compound of a catalytic metal from group VIB, and/or optionally at least one catalytic metal or compound of a catalytic metal from group VIII, in an ebullating bed process and for hydrorefining and hydroconverting hydrocarbon feeds.

FIELD OF THE INVENTION

The present invention relates to the use of a catalyst for hydrorefiningand/or hydroconverting hydrocarbon feeds (also known as hydrotreatment)in an ebullating bed reactor, the catalyst comprising an essentiallyalumina-based support in the form of extrudates, optionally at least onecatalytic metal or a compound of a catalytic metal from group VIB (group6 in the new periodic table notation), preferably molybdenum ortungsten, more preferably molybdenum, and/or optionally at least onecatalytic metal or a compound of a catalytic metal from group VIII(group 8, 9 and 10 in the new periodic table notation), preferably iron,nickel or cobalt.

The present invention thus particularly relates to the use of thecatalyst in a process for hydrorefining and/or hydroconvertinghydrocarbon feeds such as petroleum cuts, cuts originating from coal, orhydrocarbons produced from natural gas. The hydrorefining and/orhydroconversion process of the invention comprises at least onethree-phase reactor containing the hydrorefining and/or hydroconversioncatalyst in an ebullating bed.

BACKGROUND OF THE INVENTION

This type of operation has been described, for example, in U.S. Pat. No.4,251,295 or U.S. Pat. No. 4,495,060 which describe the H-OIL process.

Hydrotreatment of hydrocarbon feeds, such as sulphur-containingpetroleum cuts, is becoming more and more important in refining with theincreasing need to reduce the quantity of sulphur in petroleum cuts andto convert heavy fractions into lighter fractions which can be upgradedas a fuel. Both to satisfy the specifications imposed in every countryfor commercial fuels and for economical reasons, imported crudes whichare becoming richer and richer in heavy fractions and in heteroatoms andmore and more depleted in hydrogen must be upgraded to the best possibleextent. This upgrading implies a relatively large reduction in theaverage molecular weight of heavy constituents, which can be obtained,for example, by cracking or hydrocracking the pre-refined feeds, i.e.,desulphurized and denitrogenated feeds. Van Kessel et al explained thissubject in detail in an article published in the review "Oil & GasJournal", Feb. 16, 1987, pages 55 to 66.

The skilled person is aware that during hydrotreatment of petroleumfractions containing organometallic complexes, the majority of thosecomplexes are destroyed in the presence of hydrogen, hydrogen sulphide,and a hydrotreatment catalyst. The constituent metal of such complexesthen precipitates out in the form of a solid sulphide which then becomesfixed on the internal surface of the pores. This is particularly thecase for vanadium, nickel, iron, sodium, titanium, silicon, and coppercomplexes which are naturally present to a greater or lesser extent incrude oils depending on the origin of the crude and which, duringdistillation, tend to concentrate in the high boiling point fractionsand in particular in the residues. This is also the case for liquefiedcoal products which also comprise metals, in particular iron andtitanium. The general term hydrodemetallization (HDM) is used todesignate those organometallic complex destruction reactions inhydrocarbons.

The accumulation of solid deposits in the catalyst pores can continueuntil a portion of the pores controlling access of reactants to afraction of the interconnected pore network is completely blocked sothat that fraction becomes inactive even if the pores of that fractionare only slightly blocked or even intact. That phenomenon can causepremature and very severe catalyst deactivation. It is particularlysensitive in hydrodemetallization reactions carried out in the presenceof a supported heterogeneous catalyst. The term "heterogeneous" meansnot soluble in the hydrocarbon feed. In that case, it has been shownthat pores at the grain periphery are blocked more quickly than centralpores. Similarly, the pore mouths block up more quickly than their otherportions. Pore blocking is accompanied by a gradual reduction in theirdiameter which increasingly limits molecule diffusion and increases theconcentration gradient, thus accentuating the heterogeneity of thedeposit from the periphery to the interior of the porous particles tothe point that the pores opening to the outside are very rapidlyblocked; access to the practically intact internal pores of theparticles is thus denied to the reactants and the catalyst isprematurely deactivated.

The phenomenon described above is known as pore mouth plugging. Proof ofits existence and an analysis of its causes have been published a numberof times in the international scientific literature, for example;"Catalyst deactivation through pore mouth plugging" presented at the 5thInternational Chemical Engineering Symposium at Houston, Tex., U.S.A.,March 1978, or "Effects of feed metals on catalyst ageing inhydroprocessing residuum" in Industrial Engineering Chemistry ProcessDesign and Development, volume 20, pages 262 to 273 published in 1981 bythe American Chemical Society, or more recently in "Effect of catalystpore structure on hydrotreating of heavy oil" presented at the Nationalconference of the American Chemical Society at Las Vegas, U.S.A., Mar.30, 1982.

A catalyst for hydrotreatment of heavy hydrocarbon cuts containingmetals must thus be composed of a catalytic support with a porosityprofile which is particularly suitable for the specific diffusionalconstraints of hydrotreatment, in particular hydrodemetallization.

The catalysts usually used for hydrotreatment processes are composed ofa support on which metal oxides such as cobalt, nickel or molybdenumoxides are deposited. The catalyst is then sulphurated to transformedall or part of the metal oxides into metal sulphide phases. The supportis generally alumina-based, its role consisting of dispersing the activephase and providing a texture which can capture metal impurities, whileavoiding the blocking problems mentioned above.

Catalysts with a particular pore distribution have been described inU.S. Pat. No. 4,395,329. There are two types of prior art alumina-basedsupports. Firstly, alumina extrudates exist that are prepared from analumina gel. Hydrotreatment catalysts prepared from such extrudates havea number of disadvantages. Firstly, the process for preparing thealumina gel is particularly polluting, in contrast to that of aluminaoriginating from rapid dehydration of hydrargillite, known as flashalumina. The pores of alumina gel based supports are particularlysuitable for hydrodesulphuration and hydrotreatment of lighthydrocarbons, and not for other types of hydrotreatment. Further, eventhough such extrudates are balanced in theirhydrodemetallization/hydrodesulphuration ratio, their hydrometallizationretention capacity is low, in general at most 30% by weight, so they arerapidly saturated and have to be replaced. Further, considering the highproduction cost of the alumina gel, the manufacture of such catalysts isvery expensive.

Secondly, alumina beads prepared by rapid dehydration of hydrargillitethen agglomerating the flash alumina powder obtained are used as asupport for catalysts for hydrotreating hydrocarbon feeds containingmetals. The cost of preparing these beads is lower, however in order tomaintain it at a satisfactory level, beads with a diameter of more than2 mm have to be prepared. As a result, the metals cannot be introducedright into the core of the beads, and the catalytic phase located thereis not used.

Hydrotreatment catalyst prepared from flash alumina extrudates which aresmaller than which have a porosity which is suitable for hydrotreatmentwould not have all of those disadvantages, but there is currently noindustrial process for preparing such catalysts.

SUMMARY OF THE INVENTION

The present invention concerns the use of a catalyst for hydrotreatingcarbon-containing fractions in hydrotreatment reactions, in particularhydrogenation, hydrodenitrogenation, hydrodeoxygenation,hydrodearomatization, hydroisomerisation, hydrodealkylation,hydrodewaxing, hydrocracking, and hydrodesulphuration with ahydrodemetallization activity which is at least equivalent to that ofcatalysts currently known to the skilled person, to obtain particularlygood hydrotreatment results with respect to prior art products.

The catalyst of the invention comprises an essentially alumina-basedsupport in the form of extrudates, optionally at least one catalyticmetal or a compound of a catalytic metal from group VIB (group 6 in thenew periodic table notation), preferably molybdenum or tungsten, morepreferably molybdenum, and/or optionally, at least one catalytic metalor a compound of a catalytic metal from group VIII (group 8, 9 and 10 inthe new periodic table notation), preferably iron, nickel or cobalt,more preferably nickel.

The extruded support used in the catalyst of the invention is generallyand preferably essentially based on alumina agglomerates, the aluminaagglomerates generally and preferably being obtained by forming astarting alumina originating from rapid dehydration of hydrargillite,and generally having a total pore volume of at least 0.6 cm³ /g, anaverage mesoporous diameter in the range 15 to 36 nm (nanometers), andgenerally a quantity of alumina originating from boehmite decompositionin the range 5% to 70% by weight. The term "alumina originating fromboehmite decomposition" means that during the extrudate preparationprocess, boehmite type alumina is produced to the point of representing5% to 70% by weight of the total alumina, then decomposed. This quantityof alumina from boehmite decomposition is measured by X ray diffractionof the alumina before decomposing the boehmite.

The extruded support of the catalyst of the invention can also beobtained by extruding a mixture of varying proportions of an aluminapowder from rapid dehydration of hydrargillite (flash alumina) and atleast one alumina gel obtained, for example, by precipitating aluminiumsalts such as aluminium chloride, aluminium sulphate, aluminium nitrate,or aluminium acetate, or by hydrolysis of aluminium alkoxides such asaluminium triethoxide. Such mixtures of flash alumina and alumina gelcontain less than 50% by weight of alumina gel, preferably 1% to 45% ofalumina gel.

The catalyst used in the presence of the invention can be prepared usingany method which is known to the skilled person, more particularly usingthe methods described below.

The support is formed by alumina extrudates with a diameter generally inthe range 0.3 to 1.8 mm, preferably 0.8 to 1.8 mm, when the catalyst isused in an ebullating bed, the extrudates having the characteristicsdescribed above. Any known method can be used for the optionalintroduction of the catalytic metals, at any stage of the preparation,preferably by impregnation or co-mixing, onto the extrudates or prior totheir forming by extrusion, the optional catalytic metals being at leastone catalytic metal or a compound of a catalytic metal from group VIB(group 6 in the new periodic table notation), preferably molybdenum ortungsten, more preferably molybdenum, and/or optionally at least onecatalytic metal or a compound of a catalytic metal from group VIII(group 8, 9 and 10 in the new periodic table notation), preferably iron,nickel or cobalt, more preferably nickel. The metals can optionally bemixed with the support by co-mixing at any step of the supportpreparation process. When there are a plurality, at least part of thegroup VIB and VIII metals can optionally be introduced separately orsimultaneously during impregnation or co-mixing with the support, at anystage of forming or preparation.

As an example, the catalyst of the invention can be prepared using apreparation process comprising the following steps:

a) co-mixing alumina powder originating from rapid dehydration ofhydrargillite with at least one compound of a catalytic metal from groupVIB and/or at least one compound of a catalytic metal from group VIII,optionally followed by ageing, and/or drying, then optional calcining;

b) forming by extruding the product obtained from step a).

The metals cited above are usually introduced into the catalyst in theform of precursors such as oxides, acids, salt, or organic complexes.The sum S of the group VIB and VIII metals, expressed as the oxidesintroduced into the catalysts, is in the range 0 to 50% by weight,preferably 0.5% to 50% by weight, more preferably 0.5% to 40% by weight.It is thus possible to use the support as a catalyst without introducinga catalytic metal into the catalyst.

The preparation then generally comprises ageing and drying, thengenerally a heat treatment, for example calcining, at a temperature inthe range 400° C. to 800° C.

The support the use of which is one of the essentially elements of theinvention is essentially alumina-based. The support used in the catalystof the invention is generally and preferably obtained by forming astarting alumina originating from rapid dehydration of hydrargillite,forming preferably being carried out using one of the processesdescribed below.

Processes for preparing the support of the invention are described belowfor a support constituted by alumina. When the support contains one ormore other compounds, the compound or compounds or a precursor of thecompound or compounds may be introduced at any stage in the process forpreparing the support of the invention. It is also possible to introducethe compound or compounds by impregnating the formed alumina using thecompound or compounds or any precursor of the compound or compounds.

A first process for forming a starting alumina originating from rapiddehydration of hydrargillite comprises the following steps:

a₁ starting with an alumina originating from rapid dehydration ofhydrargillite;

b₁ rehydrating the starting alumina;

c₁ mixing the rehydrated alumina in the presence of an emulsion of atleast one hydrocarbon in water;

d₁ extruding the alumina-based paste obtained from step c₁ ;

e₁ drying and calcining the extrudates;

f₁ carrying out a hydrothermal acid treatment in a confined atmosphereon the extrudates from step e₁ ;

g₁ drying and calcining the extrudates from step f₁.

A second process for forming the alumina from a starting aluminaoriginating from rapid dehydration of hydrargillite comprises thefollowing steps:

a₂ starting from an alumina originating from rapid dehydration ofhydrargillite;

b₂ forming the alumina into beads in the presence of a pore-formingagent;

c₂ ageing the alumina beads obtained;

d₂ mixing the beads from step c₂ to obtain a paste which is extruded;

e₂ drying and calcining the extrudates obtained;

f₂ carrying out a hydrothermal acid treatment in a confined atmosphereon the extrudates obtained from step e₂ ;

g₂ drying and calcining the extrudates from step f₂.

A third process for forming an alumina from a starting aluminaoriginating from rapid dehydration of hydrargillite comprises thefollowing steps:

a₃ starting from an alumina originating from rapid dehydration ofhydrargillite;

b₃ rehydrating the starting alumina;

c₃ mixing the rehydrated alumina with a pseudo-boehmite gel, the gelbeing present in an amount in the range 1% to 30% by weight with respectto the rehydrated alumina and the gel;

d₃ extruding the alumina-based paste obtained from step c₃ ;

e₃ drying and calcining the extrudates obtained;

f₃ carrying out a hydrothermal acid treatment in a confined atmosphereon the extrudates obtained from step e₃ ;

g₃ optionally drying then calcining the extrudates from step f₃.

This process uses identical steps to steps a₁, b₁, d₁, o₁, f₁ and g₁ ofthe first process described above.

The alumina extrudates of the invention generally and preferably have atotal pore volume (TPV) of at least 0.6 cm³ /g, preferably at least 0.65cm³ /g.

The TPV is measured as follows: the grain density and absolute densityare determined; the grain densities (Dg) and absolute densities (Da) aremeasured using a mercury and helium picnometry method respectively, thenthe TPV is given by the formula: ##EQU1##

The average mesoporous diameter of the extrudates of the invention isalso generally and preferably in the range 15 to 36 nm (manometers). Theaverage mesoporous diameter for the given extrudates is measured using agraph of the pore distribution of said extrudates. It is the diameterfor which the associated volume V on the graph is: ##EQU2##

where V_(100nm) represents the volume created by pores with a diameterof over 100 nm (macropores), or the macroporous volume;

V_(6nm) represents the volume created by pores with a diameter of over 6nm.

V_(6nm) -V_(100nm) represents the mesoporous volume, i.e., the volumecreated by pores with a diameter in the range 6 nm and 100 nm, i.e., thevolume created by all the pores with a size in the range 6 nm to 100 nm(mesopores).

These volumes are measured using the mercury penetration technique inwhich the Kelvin law is applied which defines a relationship between thepressure, the diameter of the smallest pore into which the diameterpenetrates at that pressure, the wetting angle and the surface tensionin the following formula:

    φ=(4tcosθ).10/P

where

φ represents the pore diameter (in nm);

t represents the surface tension (48.5 Pa);

θ represents the angle of contact (θ=140°); and

P represents the pressure (MPa),

The extrudates of the invention preferably have a mesoporous volume(V_(6nm) -V_(100nm)) of at least 0.3 cm³ /g, more preferably at least0.5 cm³ /g.

The extrudates of the invention preferably have a macroporous volume(V_(100nm)) of at most 0.5 cm³ /g. In a variation, the macroporousvolume (V_(100nm)) is at most 0.3 cm³ /g, more preferably at most 0.1cm³ /g and still more preferably at most 0.08 cm³ /g.

These extrudates normally have a microporous volume (V_(0-6nm)) of atmost 0.55 cm³ /g, preferably at most 0.2 cm³ /g. The microporous volumerepresents the volume created by pores with a diameter of less than 6nm.

Such a pore distribution which minimises the proportion of pores of lessthan 6 nm and those of more than 100 nm while increasing the proportionof mesopores (with a diameter in the range 6 nm to 100 nm) isparticularly adapted to the diffusional constraints of hydrotreatingheavy hydrocarbon cuts.

In a preferred variation, the pore distribution over the pore diameterrange from 6 to 100 nm (mesopores) is extremely narrow at around 15 nm,i.e., in this range the diameter of the majority of pores is in therange 6 nm to 50 nm, preferably in the range 8 nm to 20 nm.

The specific surface area (SSA) of the extrudates of the invention isgenerally at least 120 m² /g, preferably at least 150 m² /g. Thissurface area is a BET surface area. The term "BET surface area" meansthe specific surface area determined by nitrogen adsorption inaccordance with the standard ASTM D 3663-78 established using theBRUNAUER-EMMETT-TELLER method described in "The Journal of the AmericanSociety" 60, 309 (1938).

Preferably, the diameter of the extrudates of the invention is in therange 0.3 to 1.8 mm, more preferably in the range 0.8 to 1.8 mm, and thelength is in the range 1 mm to 20 mm, preferably in the range 1 to 10mm, in particular when the catalyst is used in an ebullating bed.

The average crushing strength (ACS) of these extrudates is generally atleast 0.68 daN/mm for 1.6 mm extrudates, preferably at least 1 mm, andthe crush strength (CS) is at least 1 MPa. Further, the percentageattrition loss of the extrudates using American standard ASTM D4050 isgenerally less than 2.5% of the weight of the catalyst.

The method of measuring the average crushing strength (ACS) consists ofmeasuring the type of maximum compression which an extrudates cansupport before it fails, when the product is placed between two planesbeing displaced at a constant speed of 5 cm/min.

Compression is applied perpendicular to one of the extrudategeneratrices, and the average crushing strength is expressed as theratio of the force to the length of the generatrix of the extrudate.

The method used to measure the crush strength (CS) consists ofsubjecting a certain quantity of extrudates to an increasing pressureover a sieve and recovering the fines resulting from crushing theextrudates. The crush strength corresponds to the force exerted toobtain fines representing 0.5% of the weight of the extrudates undertest. The attrition test using standard ASTM D4058 consists of rotatinga sample of catalyst in a cylinder. The attrition losses are thencalculated using the following formula:

% attrition loss=100(1-weight of catalyst over 0.6 mm after test/wt ofcatalyst of more than 0.6 mm charged into cylinder).

The alumina of the invention is essentially constituted by a pluralityof juxtaposed agglomerates, each of these agglomerates generally andpreferably being partially in the form of packs of flakes and partiallyin the form of needles, the needles being uniformly dispersed botharound the packs of flakes and between the flakes.

In general, the length and breadth of the flakes varies between 1 and 5μm with a thickness of the order of 10 nm. They can be packed in groupsforming a thickness of the order of 0.1 to 0.5 μm, the groups possiblybeing separated from each other by a thickness of the order of 0.05 to0.1 μm.

The needle length can be in the range 0.05 to 0.5 μm; their crosssection is of the order of 10 to 20 nm. These dimensions are given bymeasuring the extrudates in electron microscope photographs. The aluminaflakes principally comprise χ alumina and η alumina and the needles areγ alumina.

The flake structure is characteristic of the hydrargillite lineage ofalumina, which means that before activation by calcining, theseextrudates have the same structure, the flakes being hydrargillite innature. On calcining, this alumina in its hydrargillite form isprincipally transformed into dehydrated χ and η aluminas

In contrast, the needle structure is characteristic of a boehmitelineage, meaning that before activation by calcining, these extrudateshave the same structure, this alumina being in the form of boehmite.Calcining transforms this boehmite alumina into dehydrated γ alumina.

The extrudates of the invention are thus obtained by calcining, theextrudates being constituted by hydrargillite alumina-based flakes priorto calcining, the flakes being surrounded at their periphery by boehmitealumina-based needles.

The forming process of the invention is more preferably suitable for astarting alumina originating from rapid dehydration of Bayer hydrate(hydrargillite) which is an industrially available aluminium hydroxideand extremely cheap.

Such an alumina is in particular obtained by rapid dehydration ofhydrargillite using a hot gas stream, the temperature of the gasentering the apparatus generally being between about 400° C. and 1200°C., the contact time between the alumina and the hot gases generallybeing in the range from a fraction of a second to 4-5 seconds; such aprocess for preparing an alumina powder has been described in Frenchpatent FR-A1-1 108 011.

The alumina obtained can be used as it is or before undergoing step b₁,it can be treated to eliminate the alkalis present; a Na₂ O content ofless than 0.5% by weight is preferable.

The starting alumina is preferably re-hydrated during step b₁ so thatthe boehmite type alumina content is at least 3% by weight, preferablyat most 40% by weight.

The various steps of these processes for preparing alumina extrudatesare described in more detail in a patent application entitled "Aluminaextrudates, processes for their preparation and their use as catalystsor catalyst supports" by Rhone-Poulene Chimie.

The catalysts used in the process of the invention can thus be used inall processes for hydrorefining and hydroconverting hydrocarbon feedssuch as petroleum cuts, cuts originating from coal, extracts frombituminous sands and bituminous schists, or hydrocarbons produced fromnatural gas, more particularly for hydrogenation, hydrodenitrogenation,hydrodeoxygenation, hydrodearomatisation, hydroisomerisation,hydrodealkylation, hydrodewaxing, dehydrogenation, hydrocracking,hydrodesulphuration and hydrodemetallization of carbon-containing feedscontaining aromatic compounds and/or olefinic compounds and/ornaphthenic compounds and/or paraffinic compounds, the feeds possiblycontaining metals and/or nitrogen and/or oxygen and/or sulphur. Inparticular, by modifying the parameters for preparing the essentiallyalumina-based support, it is possible to obtain different poredistributions and thus to modify the hydrodesulphuration (HDS) andhydrodemetallization (HDM) proportions.

Hydrorefining and hydroconversion of hydrocarbon feeds (hydrotreatment)can be carried out in a reactor containing the catalyst of the inventionin an ebullating bed. Such hydrotreatments can be applied, for example,to petroleum fractions such as crude oils with an API degree of lessthan 20, bituminous sand extracts and bituminous schists, atmosphericresidues, vacuum residues, asphalts, deasphalted oils, deasphaltedvacuum residues, deasphalted crudes, heavy fuels, atmosphericdistillates and vacuum distillates, or other hydrocarbons such asliquefied coal products. In an ebullating bed process, thehydrotreatments designed to eliminate impurities such as sulphur,nitrogen or metals, and to reduce the average boiling point of thesehydrocarbons are normally carried out at a temperature of about 320° C.to about 470° C., preferably about 400° C. to about 450°, at a partialpressure of hydrogen of about 3 (megapascals) to about 30, preferably 5to 20 at a space velocity of about 0.1 to about 6 volumes of feed pervolume of catalyst per hour, preferably 0.5 to 2 volumes per volume ofcatalyst per hour, the ratio of gaseous hydrogen to the liquidhydrocarbon feed being in the range 100 to 3000 standard cubic metersper cubic meter (Sm³ /m³), preferably between 200 and 1200.

The following examples illustrate the invention without limiting itsscope.

EXAMPLE 1

Preparation of alumina support A forming part of the composition ofcatalysts A1 and A2 of the invention

Step a₁ --starting alumina: The starting material was alumina obtainedby very rapid decomposition of hydrargillite in a hot air stream(T=1000° C.). The product obtained was constituted by a mixture oftransition aluminas; (khi) and (rho) aluminas. The specific surface areaof the product was 300 m² /g and the loss on ignition (LOI) was 5%.

Step b₁ --rehydration: The alumina was rehydrated by taking it intosuspension in water at a concentration of 500 g/l at a temperature of90° C. for a period of 48 h in the presence of 0.5% citric acid.

After filtering the suspension, a cake of alumina was recovered whichwas washed with water then dried at a temperature of 140° C. for 24 h.

The alumina obtained was in the form of a powder, its loss on ignition(LOI), measured by calcining at 1000° C., and its amount of alumina inthe form of boehmite, measured by X ray diffraction, are shown in Table1.

Step c₁ --mixing: 10 kg of rehydrated and dried powder was introducedinto a 25 l volume Z blade mixer and an emulsion of hydrocarbon in waterstabilised by a surfactant, obtained using a stirred reactor, and 100%nitric acid, was gradually added. The characteristics are shown in Table1.

Mixing was maintained until a consistent homogeneous paste was obtained.

After mixing, a 20% ammonia solution was added to neutralise the excessnitric acid, containing mixing for 3 to 5 min.

Step d₁ --extrusion: The paste obtained was introduced into a singlescrew extruder to obtain raw extrudates with a diameter of 1.6 mm.

Step e₁ --drying/calcining: The extrudates were then dried at 140° C.for 15 h and calcined for 2 h at the temperature shown in Table 1. Thecalcined support had a specific surface area which was adjusted tobetween 200 m² /g and 130 m² /g as indicated in Table 1.

Step f₁ --hydrothermal treatment: The extrudates obtained wereimpregnated with a solution of nitric and acetic acid in the followingconcentrations: 3.5% of nitric acid with respect to the weight ofalumina and 6.5% of acetic acid with respect to the weight of alumina.They were underwent hydrothermal treatment in a rotating basketautoclave under the conditions defined in Table 1.

Step g₁ --drying/calcining: At the end of this treatment, the extrudateswere calcined at a temperature of 550° C. for 2 h.

The characteristics of the extrudates obtained are shown in Table 1.

The amount of boehmite was measured for the extrudates before finalcalcining.

                  TABLE 1                                                         ______________________________________                                                   Alumina A                                                                              Alumina B Alumina C                                       ______________________________________                                        Rehydrated alumina - end of step a1                                           % boehmite   33         24        33                                          LOT (1000° C.)                                                                      25         25        23                                          Mixing - step b1                                                              Hydrocarbon type                                                                           petroleum  petroleum petroleum                                   % HNO3/Al2O3 10         10        10                                          % hydrocarbon/Al2O3                                                                        5          15        15                                          water/hydrocarbon                                                                          3.7        3.5       2.6                                         Surfactant type                                                                            Galoryl EM Galoryl EM                                                                              Soprophor                                                10         10        SC138                                       % surfactant/hydrocarbon                                                                   150        17        15                                          % neutralisation with                                                                      65         65        65                                          respect to HNO3,                                                              equivalents                                                                   Drying/calcining - step d1                                                    Calcining temperature                                                                      600        680       600                                         (° C.)                                                                 Specific surface area                                                                      260        148       177                                         (m.sup.2 /g)                                                                  Hydrothermal treatment - step e1                                              Temperature (° C.)                                                                  212        212       178                                         Pressure (MPa)                                                                             19         19        10                                          Time (h)     2          2         2                                           % boehmite   45         40        9                                           Characteristics of calcined extrudates obtained                               TPV (cm.sup.3 /g)                                                                          0.86       0.80      0.64                                        V corresponding to                                                                         0.62       0.59      0.50                                        6 < Dp < 100 nm                                                               (cm.sup.3 /g)                                                                 V corresponding to                                                                         0.28       0.19      <0.02                                       Dp > 100 nm                                                                   (cm.sup.3 /g)                                                                 av. mesopore diameter                                                                      8.5        28        16                                          (nm)                                                                          V corresponding to                                                                         0.01       0.02      0.14                                        Dp < 6 nm                                                                     (cm.sup.3 /g)                                                                 Specific surface area                                                                      300        140       174                                         (m.sup.2 /g)                                                                  ACS (daN/mm) 0.9        1.2       0.7                                         CS (MPa)     1.2        1.58      1.46                                        ______________________________________                                    

EXAMPLE 2

Preparation of catalyst A1 (in accordance with the invention)

We dry impregnated the extruded support A of Example 1 with an aqueoussolution containing molybdenum and nickel salts. The molybdenum salt wasammonium heptamolybdate Mo₇ O₂₄ (NH₄)₅.4H₂ O and the nickel salt wasnickel nitrate Ni(NO₃)₂.6H₂ O. After ageing at room temperature in awater-saturated atmosphere, the impregnated extrudates were driedovernight at 120° C. then calcined at 550° C. for 2 hours in air. Thefinal molybdenum trioxide content was 12.5% by weight and that of nickeloxide NiO was 3.0% by weight.

The attrition resistance of the catalyst was evaluated in a rotatingdrum in accordance with ASTM D4058. The attrition loss was thencalculated using the following formula:

% attrition loss=100(1-wt of catalyst of over 0.6 mm after test/weightof catalyst over 0.6 mm charged into cylinder).

Catalyst A1 had an attrition loss percentage of 0.30% of the weight ofthe catalyst.

EXAMPLE 3

Preparation of catalyst A2 (in accordance with the invention)

We dry impregnated the extruded support of Example 1 with an aqueoussolution containing molybdenum salts. The molybdenum salt was ammoniumheptamolybdate Mo₇ O₂₄ (NH₄)₆.4H₂ O. After ageing at room temperature ina water-saturated atmosphere, the impregnated extrudates were driedovernight at 120° C. then calcined at 550° C. for 2 hours in air. Thefinal molybdenum trioxide content was 12.8%.

Catalyst A2 had an attrition loss percentage of 0.32% of the weight ofthe catalyst, calculated using the attrition test described in Example2.

EXAMPLE 4

Preparation of alumina support B forming part of the composition ofcatalyst B of the invention

The alumina constituting this support was prepared using the samesequence of steps as the alumina of support A but using differentconditions during the mixing step and the drying/calcining step afterextrusion (see Table 1).

The characteristics of the extrudates obtained are shown in Table 1.

The amount of boehmite was measured for the extrudates before finalcalcining.

EXAMPLE 5

Preparation of catalyst B (in accordance with the invention)

We dry impregnated the extruded support of Example 4 with an aqueoussolution containing molybdenum and nickel salts. The molybdenum salt wasammonium heptamolybdate Mo₇ O₂₄ (NH₄)₆.4H₂ O and the nickel salt wasnickel nitrate Ni(NO₃)₂.6H₂ O. After ageing at room temperature in awater-saturated atmosphere, the impregnated extrudates were driedovernight at 120° C. then calcined at 550° C. for 2 hours in air. Thefinal molybdenum trioxide content was 6.5% by weight and that of nickeloxide NiO was 1.5% by weight.

Catalyst B had an attrition loss percentage of 0.50% of the weight ofthe catalyst, calculated using the attrition test described in Example2.

EXAMPLE 6 Preparation of alumina support C forming part of thecomposition of catalysts C1 and C2 in accordance with the invention.

The same steps of Example 1 were used except that mixing step b₁ wascarried out as follows.

Step b₁ --mixing: This was a continuous process carried out in aco-rotating twin screw mixer.

Upstream of the mixer, the rehydrated and dried alumina was introducedat a rate of 90 kg/h. An emulsion of petroleum in water was prepared ina stirred reactor, by introducing:

5.46 kg of water;

10.04 kg of 69% nitric acid;

10.4 kg of petroleum;

1.56 kg of Soprophor SC138.

This emulsion was introduced into the primer of the twin screw machineat a rate of 27.46 kg/h immediately following introduction of thealumina powder.

After machining, a 28% ammonia solution was introduced at a rate of 4.34kg/h.

The passage time for the powder in the machine was of the order of 50 to60 s.

A homogeneous paste which could be extruded was obtained from themachine outlet.

The characteristics of the extrudates obtained are shown in Table 1.

The boehmite content was measured for the extrudates prior to finalcalcining.

EXAMPLE 7

Preparation of catalyst C1 (in accordance with the invention)

We dry impregnated the extruded support of Example 6 with an aqueoussolution containing molybdenum and nickel salts. The molybdenum salt wasammonium heptamolybdate Mo₇ O₂₄ (NH₄)₆.4H₂ O and the nickel salt wasnickel nitrate Ni(NO₃)₂.6H₂ O. After ageing at room temperature in awater-saturated atmosphere, the impregnated extrudates were driedovernight at 120° C. then calcined at 550° C. for 2 hours in air. Thefinal molybdenum trioxide content was 13.0% by weight and that of nickeloxide NiO was 3.2% by weight.

Catalyst C1 had an attrition loss percentage of 0.35% of the weight ofthe catalyst, calculated using the attrition test described in Example2.

EXAMPLE 8

Preparation of catalyst C2 (in accordance with the invention)

We dry impregnated the extruded support of Example 6 with an aqueoussolution containing nickel salts. The nickel salt was nickel nitrateNi(NO₃)₂.6H₂ O. After ageing at room temperature in a water-saturatedatmosphere, the impregnated extrudates were dried overnight at 120° C.then calcined at 550° C. for 2 hours in air. The final nickel oxide NiOwas 5.9% by weight.

Catalyst C2 had an attrition loss percentage of 0.33% of the weight ofthe catalyst, calculated using the attrition test described in Example2.

EXAMPLE 9

Preparation of alumina support D forming part of the composition ofcatalyst D (comparative)

The alumina constituting support D was prepared using the sameprocedures as support A except that hydrothermal treatment step e1 wasomitted.

The characteristics of the calcined extrudates are shown in Table 2.

    ______________________________________                                                          Alumina D                                                   ______________________________________                                        TPV (cm.sup.3 /g)   0.82                                                      V corresponding to 6 <D.sub.p <100                                                                0.08                                                      nm (cm.sup.3 /g)                                                              V corresponding to D.sub.p > 100 nm                                                               0.38                                                      (cm.sup.3 /g)                                                                 av. mesopore diameter (nm)                                                                        5.8                                                       V corresponding to D.sub.p < 6 nm                                                                 0.33                                                      (cm.sup.3 /g)                                                                 SSA (m.sup.3 /g)    228                                                       ACS (daN · mm)                                                                           0.7                                                       CS (MPa)            0.6                                                       ______________________________________                                    

EXAMPLE 10

Preparation of catalyst D (comparative)

We dry impregnated the extruded support of Example 9 with an aqueoussolution containing molybdenum and nickel salts. The molybdenum salt wasammonium heptamolybdate Mo₇ O₂₄ (NH₄)₆.4H₂ O and the nickel salt wasnickel nitrate Ni(NO₃)₂.6H₂ O. After ageing at room temperature in awater-saturated atmosphere, the impregnated extrudates were driedovernight at 120° C. then calcined at 550° C. for 2 hours in air. Thefinal molybdenum trioxide content was 10.2% by weight and that of nickeloxide NiO was 2.5% by weight.

Catalyst D had an attrition loss percentage of 0.6% of the weight of thecatalyst, calculated using the attrition test described in Example 3.

EXAMPLE 11

Hydroconversion tests for petroleum residues using catalysts A1, A2, B,C1, C2 and D

Catalysts A1, A2, B, C1, C2 and D described above were compared in apilot unit comprising a tube reactor provided with an apparatus forpermanently maintaining ebullation of the catalyst inside the reactor.The pilot unit was representative of an industrial H-Oil ebullating bedresidue hydroconversion reactor described in a number of patents, forexample U.S. Pat. No. 4,521,295 and U.S. Pat. No. 4,495,060.

The pilot reactor was charged with 1 liter of catalyst in extrudate formas described above. Once in an ebullating bed mode, the expandedcatalyst occupied a volume of 1.5 l in the reactor.

    ______________________________________                                        The feed used was                                                             a heavy Arabian vacuum                                                        residue with the                                                              characteristics given in the                                                  following table.         Arabian heavy VR                                     ______________________________________                                        Density 15/4             1.0457                                               Viscosity at 100° C.                                                                    mm.sup.2 /g                                                                           5110                                                 Viscosity at 150° C.                                                                    mm.sup.2 /g                                                                           285                                                  Sulphur          % by wt 5.39                                                 Nitrogen         % by wt 0.46                                                 Nickel           ppm     60                                                   Vanadium         ppm     163                                                  Carbon           % by wt 84.5                                                 Hydrogen         % by wt 9.56                                                 Aromatic carbon  %       37.9                                                 Molecular weight g/mol   1060                                                 Conradson carbon % by wt 24                                                   Asphaltenes C5   % by wt 24.7                                                 Asphaltenes C7   % by wt 14.5                                                 SARA             % by wt                                                      Saturates        % by wt 7.2                                                  Aromatics        % by wt 38.2                                                 Resins           % by wt 37.1                                                 Asphaltenes      % by wt 14.5                                                 Simulated distillation                                                        IP               ° C.                                                                           404                                                  5%               ° C.                                                                           510                                                  10%              ° C.                                                                           545                                                  20%              ° C.                                                                           585                                                  BP               ° C.                                                                           613                                                  % dist           % by wt 29                                                   Softening point  ° C.                                                                           49                                                   ______________________________________                                    

The unit was operated with the above residue under the followingoperating conditions:

pressure=16 MPa;

hydrogen flow rate: 600 std l. H₂ /l of feed;

hourly space velocity=0.3 m³ of feed/m³ of reactor/h⁻¹.

The temperature was adjusted to about 420-430° C. so that all of thecatalysts led to 65% by weight conversion of the 550° C.⁺ fraction.

The HDS and HDM performances were compared after 2 weeks of test.

The HDS ratio is defined as follows:

HDS (wt %)=((wt % S)feed-(wt % S)test/(wt % S)feed * 100

The HDM ratio is defined as follows:

HDM (wt %)=((ppm wt Ni+V)feed-(ppm wt Ni+V)test)/(ppm wt Ni+V)feed≠100.

The degree of conversion is defined as follows:

Conversion (wt %)=((wt % of 550° C.+)feed-(wt % of 550° C.+)test)/(% wt% of 550° C.+)feed≠100.

The stability of the products obtained was evaluated using a "P valueShell" method carried out on the 350° C.⁺ fraction of the effluentrecovered after the test.

The following table compares the HDS, HDM and P Value Shell valuesobtained with catalysts A1, A2, B, C1, C2 and D for 65% by weight ofconversion of the 550° C.⁺ fraction.

    ______________________________________                                        Catalyst  HDS (wt %)  HDM (wt %)                                                                              P Value Shell                                 ______________________________________                                        Catalyst A1                                                                             82          85        1.1                                           Catalyst A2                                                                             78          82        1.1                                           Catalyst B                                                                              72          92        1.2                                           Catalyst C1                                                                             84          85        1.4                                           Catalyst C2                                                                             78          83        1.2                                           Catalyst D                                                                              72          78        1.1                                           ______________________________________                                    

It thus appears that the catalysts in the form of extrudates of thepresent invention can achieve high degrees of conversion of the 550° C.⁺fraction of an oil residue and result in stable products. Thesecatalysts can also significantly hydrodesulphurise and hydrodemetallisethe residue and produce light fractions (diesel, gasoline) which satisfyrefiners' specifications. By adjusting the alumina preparationparameters, it is possible to obtain different pore distributions andthus modify the degrees of HDS, HDM and certain petroleum qualities ofthe effluents from the units such as the stability of the residual 350°C.⁺ fraction.

The preceding examples can be repeated with similar success bysubstituting the generically or specifically described reactants and/oroperating conditions of this invention for those used in the precedingexamples.

The entire disclosure of all applications, patents and publications,cited above, and of corresponding French application No. 97/07150, arehereby incorporated by reference.

From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention, and withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions.

What is claimed is:
 1. A process for hydrotreating a hydrocarbon feedwith a catalyst used in an ebullating bed, in the presence of hydrogenunder hydrotreating conditions, the catalyst comprising an essentiallyalumina-based extruded support, essentially constituted by a pluralityof juxtaposed agglomerates, optionally at least one catalytic metal or acompound of a catalytic metal from group VIB (group 6 of the newperiodic table notation) and/or optionally, at least one catalytic metalor a compound of a catalytic metal from group VIII (group 8, 9 and 10 ofthe new periodic table notation, in which the sum S of the group VIB andVIII metals, expressed as the oxides, is in the range 0% to 50% byweight, and characterized in that each of said agglomerates is partly inthe form of packs of flakes and partly in the form of needles, saidneedles being uniformly dispersed both about the packs of flakes andbetween the flakes.
 2. A process according to claim 1, in which thecatalyst contains no metals (S=0% by weight.
 3. A process according toclaim 1, in which the sum S is in the range 0.5% to 50% by weight.
 4. Aprocess to claim 1, in which the alumina-based agglomerates are obtainedby forming a starting alumina originating from rapid dehydration ofhydrargillite.
 5. A process according to claim 1, said catalyst having atotal pore volume of at least 0.6 cm³ /g, an average diameter ofmesopores in the range 15 to 36 nm; a mesoporous volume V_(6nm)-V_(100nm) of at least 0.3 cm³ /g, a macroporous volume V_(100nm) of atmost 0.5 cm³ /g and a microporous volume V_(0-6nm) of at most 0.55 cm³/g.
 6. A process according to claim 1 in which the group VIB metal ismolybdenum or tungsten, and the group VIII metal is iron, nickel, orcobalt.
 7. A process according to claim 1 in which the group VIB metalis molybdenum, and the group VIII metal is nickel.
 8. A processaccording to claim 1, in which the catalyst is in the form of aluminaextrudates having a diameter in the range 0.3 to 1.8 mm.
 9. A processaccording to claim 1, wherein the alumina is produced by the followingsteps:a₁ starting with an alumina originating from rapid dehydration ofhydrargillite; b₁ rehydrating the starting alumina; c₁ mixing therehydrated alumina with an emulsion of at least one hydrocarbon inwater; d₁ extruding the alumina-based paste obtained from step c₁ ; e₁drying and calcining the extrudates from step d₁ ; f₁ carrying out ahydrothermal acid treatment in a confined atmosphere on the extrudatesfrom step e₁ ; g₁ drying and calcining the extrudates from step f₁. 10.A process according to claim 1, wherein the alumina is produced by thefollowing steps:a₂ starting from an alumina originating from rapiddehydration of hydrargillite; b₂ forming the alumina into beads in thepresence of a pore-forming agent; c₂ ageing the alumina beads obtained;d₂ mixing the beads from step c₂ to obtain a paste which is extruded; e₂drying and calcining the extrudates from step d₂ ; f₂ carrying out ahydrothermal acid treatment in a confined atmosphere on the extrudatesobtained from step e₂ ; g₂ drying and calcining the extrudates from stepf₂.
 11. A process according to claim 1, wherein the alumina is producedby the following steps:a₃ starting from an alumina originating fromrapid dehydration of hydrargillite; b₃ rehydrating the starting alumina;c₃ mixing the rehydrated alumina with a pseudo-boehmite gel, said gelbeing present in an amount in the range 1% to 30% by weight with respectto the rehydrated alumina and the gel; d₃ extruding the alumina-basedpaste obtained from step c₃ ; e₃ drying and calcining the extrudatesfrom step d₃ ; f₃ carrying out a hydrothermal acid treatment in aconfined atmosphere on the extrudates obtained from step e₃ ; g₃optionally drying, then calcining the extrudates from step f₃.
 12. Aprocess according to claim 1, in which the hydrocarbon feed includes atleast one of vanadium, nickel, sodium, titanium, silica, and copper. 13.A process according to claim 1, in which the hydrocarbon feed includesat least one of sulphur, nitrogen, and oxygen.
 14. A process to claim 1,in which the hydrotreatment process is carried out at a temperature of320° C. to about 450° C., at a partial pressure of hydrogen of about 3MPa to about 30 MPa, at a space velocity of about 0.1 to about 5 volumesof feed per volume of catalyst per hour, the ratio of gaseous hydrogenover the liquid hydrocarbon feed being in the range of 200 to 5000standard cubic meters per cubic meter (Sm³ /m³).
 15. A process accordingto claim 5, wherein the group VIB metal is molybdenum or tungsten andthe group VIII metal is iron, nickel, or cobalt; and the alumina-basedagglomerates are obtained by forming a starting alumina originating fromrapid dehydrogenation of hydrargillite.